(1) Field of the Invention
The present invention relates generally to acoustic processing, and more particularly to an acoustic processing method that can be used to estimate the size of small objects in a fluid medium.
(2) Description of the Prior Art
It is difficult to generate an image of an object using acoustic echoes when the object size is on the order of the wavelength of the acoustic radiation used to generate the echoes. At lower frequencies, or smaller sizes, scattering becomes less “specular” and more “diffracting” in nature. While there have been some successful efforts involving the imaging of small objects in the near field, the technique cannot be extended to the imaging of small objects in the far field. If such far field imaging could be achieved, it could be used in medical acoustic, sonar, and particle detection on semiconductor wafer evaluation applications. In each of these applications, it may also be desirable to know the size of the small object, e.g., a tumor or other physical abnormality in medical acoustic applications, a mine-like object in sonar applications, and an imperfection in a semiconductor in wafer evaluation applications.